What is the range of the function \(f(x)=\operatorname{sgn}(x)\)?

Correct answer: \(\{-1,0,1\}\)

For the signum function, \(\operatorname{sgn}(x)=-1\) for \(x<0\), \(\operatorname{sgn}(x)=0\) for \(x=0\), and \(\operatorname{sgn}(x)=1\) for \(x>0\). Hence, the function takes only the three values \(-1,0,1\), so its range is \(\{-1,0,1\}\). Option D omits \(-1\), which occurs for negative values of \(x\). Exam tip: evaluate the three cases \(x<0\), \(x=0\), and \(x>0\) for every signum-function question.